四角切圆燃煤锅炉不同燃尽风量下的燃烧特性数值模拟

Numerical Simulation of Combustion Characteristics on Tangentially-Fired Boiler with Variable Over-Fire-Air Distribution

对某300 MW机组四角切圆燃煤锅炉进行燃尽风配风方式的数值模拟,将模拟结果与实际检测结果进行对比,验证了模型的准确性。模拟结果表明,炉内燃烧温度分布均匀,未出现火焰偏斜、冲墙等现象;在负荷一定的情况下增加燃尽风量,有利于降低排放的NO_x质量浓度;在高负荷下4台磨煤机运行时,应尽量开大上级燃尽风门开度,进一步降低NO_x质量浓度,而飞灰中碳质量分数和煤粉燃尽率等指标变化较小;在较低负荷下3台磨煤机运行时,在保证一定燃尽风量的条件下,应尽量运行下级燃尽风而停运上级燃尽风,不仅有利于维持较低的NO_x质量浓度,而且可以保证锅炉的燃烧效率。

A numerical simulation has been carried out to evaluate the characteristics ofcombustion and NOx emissions in a 300 MW tangentially fired utility boiler with variableover-fire-air distribution. The numerical simulation was validated using the measured databefore the combustion modification with a good agreement. The simulation results showthat, the combustion temperature in the furnace is evenly distributed, and there is nodeviation of flame or wall. Under a certain load, increasing the rate of over-fire-air, and itis conducive to reducing NOx emissions. In high-load operating condition with 4 coalgrinders running, the upper level over-fire-air door should be opened as far as possible tofurther reduce NOx, while the carbon content of fly ash and coal burnout rate have littlechange. When in low-load operating condition with 3 coal grinders running, it′s a betteroperation to run lower level over-fire-air while stop higher level over-fire-air with totalover-fire-air rate is constant to maintain the NOx emission at a low level while ensuringthe boiler combustion efficiency.